Expand all paths to be based off pdfium/ directory

core/src/fpdfdoc/doc_vtmodule.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/include/fpdfdoc/fpdf_doc.h"
 #include "core/include/fpdfdoc/fpdf_vt.h"
-#include "pdf_vt.h"
+#include "core/src/fpdfdoc/pdf_vt.h"
 
 IPDF_VariableText* IPDF_VariableText::NewVariableText() {
   return new CPDF_VariableText();
 }
 void IPDF_VariableText::DelVariableText(IPDF_VariableText* pVT) {
   delete (CPDF_VariableText*)pVT;
 }